1. Technical Field
The present invention relates to a method of manufacturing a semiconductor device in which a functional portion of an element is exposed.
2. Related Art
In recent years, with the development of technology, a semiconductor device in which a functional portion of an element is exposed has come into practical use. In a semiconductor device in which an optical signal is directly input from the outside of the semiconductor device to a light receiving portion of an optical element that converts the optical signal into an electric signal, there is a demand for a structure capable of preventing the attenuation of the optical signal, improving the humidity resistance of the semiconductor device by using a black resin, and obtaining appropriate reflow conditions during lead-free mounting.
In particular, in an optical recording technique using blue light as an optical signal, an epoxy resin used for a light receiving device that converts an optical signal into an electric signal is deteriorated by blue light and the light transmission characteristics of the epoxy resin with respect to the blue light are lowered. As a result, the light receiving device is not available. Therefore, a semiconductor device is required in which an epoxy resin is removed from an optical path to expose the functional portion.
It is expected that the semiconductor device having the above-mentioned structure will be applied to a MEMS (micro electro-mechanical system), an apparatus in which a movable portion is provided in a functional element, such as an electromechanical acoustic filter, and the movable portion is not sealed with a resin, and a solid-state imaging element for a camera.
FIGS. 7A to 7F are cross-sectional views illustrating a method of manufacturing an imaging semiconductor device in which an epoxy resin is removed from an optical path to expose a functional portion, which is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2006-237051. FIGS. 8A to 8G are cross-sectional views illustrating a method of manufacturing an imaging semiconductor device in which an epoxy resin is removed from an optical path to expose a functional portion, which is disclosed in JP-A No. 2003-332542.
In JP-A No. 2006-237051, as shown in FIG. 7A, a photoresist is applied onto functional portions of a semiconductor wafer 1 having a plurality of semiconductor elements 5 provided thereon, and exposure, development, and etching are performed on the resist to form a resist protective film 2. Then, dicing is performed to obtain the semiconductor elements 5. Then, as shown in FIGS. 7B and 7C, the semiconductor elements 5 each having the resist protective film 2 formed thereon are mounted on a circuit board 6, and the semiconductor elements 5 and the circuit board 6 are electrically connected to each other by wires 7. Then, as shown in FIG. 7D, resin sealing is performed to cover the semiconductor elements 5, the wires 7, and the protective film 2 with a resin 8. The upper surface of the protective film 2 is also covered with the resin 8.
Then, as shown in FIG. 7E, the resin is polished to expose the protective film 2. The exposed protective film 2 is removed by etching to expose the functional portions of the semiconductor elements 5.
Then, as shown in FIG. 7F, a cover glass (cover tape) 11 is provided in order to protect the functional portions, and the semiconductor elements are individually cut. In this way, an imaging semiconductor device is completed.
In JP-A No. 2003-332542, as shown in FIG. 8A, solid-state imaging elements 10 are individually bonded to a base 30 at desired positions. Then, as shown in FIG. 8B, flexible protective films 36 are individually formed to cover light receiving regions of the exposed surfaces of the solid-state imaging elements 10.
Then, as shown in FIG. 8C, the base 30 is electrically connected to the solid-state imaging elements 10 by metal wires 40. Then, as shown in FIG. 8D, a mold having a flat pressing surface is used to press the solid-state imaging elements 10 having the protective films 36 formed thereon together with the base 30 to fill a gap portion surrounded by the pressing surface of the mold, the protective films 36, and adjacent solid-state imaging elements 10 with a sealing material 42.
Then, as shown in FIG. 8E, after the resin molding, the protective film 36 is removed. Then, as shown in FIG. 8F, a light transmitting plate 46 is adhered to the entire surface of the base 30, with the sealing material 42 interposed therebetween, so as to cover the exposed light receiving surface of each of the solid-state imaging elements 10. Then, the adjacent solid-state imaging elements 10 are cut along a cut line therebetween to obtain individual semiconductor devices.
However, when the method disclosed in JP-A No. 2006-237051 is used, some problems arise.
The following problems are all caused by a process of polishing the resin 8 covering the upper surface of the protective film 2 before the resist protective film 2 is removed. The upper surface of the protective film 2 needs to be covered with the resin 8 for the following reason. When the protective film 2 is made of a photoresist with a thickness of 0.1 mm or more by a coating method, there is a variation in the thickness of the film, and it is difficult to uniformly clamp the protective film 2 with the sealing mold during resin sealing. Therefore, it is necessary to cover the upper surface of the protective film 2 with the resin 8. The problems will be described below.
The first problem is that a process of polishing the resin 8 is needed, which results in a reduction in productivity.
The addition of the polish process causes an increase in the number of manufacturing processes and an increase in manufacturing time. In particular, the polish process requires a preparation process of mounting a semiconductor device to be polished to a supporting member, and a post-process of taking off the polished thin semiconductor device from the supporting member. Therefore, processes other than the polish process are added. As a result, the manufacturing time is greatly affected by the addition of the processes.
The second problem is that the quality of the semiconductor device deteriorates.
When the resin 8 is polished by the above-mentioned resin polishing process, the wiring lines are cut or, in worse cases, the semiconductor elements are damaged due to vibration caused by the polishing process. As a result, the quality of the semiconductor device deteriorates.
In the method disclosed in JP-A No. 2003-332542, manufacturing costs increase for the following reason.
In JP-A No. 2003-332542, the protective films 36 are individually adhered to the solid-state imaging elements 10. The individual protective films 36 have flexibility, and the solid-state imaging elements 10 are accurately mounted to the base 30 at desired positions in advance.
Therefore, the protective films 36 need to be individually adhered to the solid-state imaging elements mounted on the base with high accuracy.
In order to accurately adhere the individual flexible protective films 36 to the light receiving regions of the solid-state imaging elements 10 mounted on the base 30, for example, it is necessary to use a camera to detect the positions of both the protective films 36 and the solid-state imaging elements 10 and individually control them to perform adhesion therebetween. That is, expensive facilities are used to adhere the protective films 36, and it is necessary to detect the positions of the protective films and the solid-state imaging elements in order to perform adhesion therebetween. Therefore, a certain amount of time is required for the adhesion, and a manufacturing TAT increases.
As described above, In JP-A No. 2003-332542, expensive facilities and time are required for the process of adhering the protective film. Therefore, it is easily expected that productivity will be lowered and manufacturing costs will increase. When the facilities are not provided and the time for adhesion is not sufficient, the position accuracy of the protective film 36 is lowered, and yield is lowered. As a result, manufacturing costs increase.
In addition, the protective films 36 are individually supplied in advance. Therefore, the cost of the protective film increases.